Processes for the recovery of precious metals, and particularly platinum group metals, continue to be developed and refined. These processes, however, often suffer in both quantitative and qualitative efficiency due to impurities and interfering metals, salts and, ions, in the feed stream that are not sufficiently separated from the target metal species.
A hydrometallurgical process for the recovery of precious metals selected from platinum [Pt], palladium [Pd], rhodium [Rh], ruthenium [Ru], iridium [Ir], osmium [Os] and gold [Au] from basic metals in an acidic aqueous halide solution is described in U.S. Pat. No. 7,935,173, which is incorporated herein, by reference. In that process, substituted quaternary ammonium salts are used to precipitate platinum group metal(s) for separation. This process suffers however, from significantly low recovery of the target precious metals, in both quantitative and qualitative terms, in instances in which a feed stream containing lead, iron, nickel, selenium, tellurium, sulfur, arsenic, or combinations of these compounds is present.
Thus, there is a need for a precious metals recovery process sufficiently robust to provide quantitative and qualitative recovery in the presence of such impurities as interfering metals, salts and, ions, including specifically lead, iron, nickel, selenium, tellurium, sulfur, arsenic, or combinations of these compounds is present.